During drilling operations a drill bit is attached to the bottom end region of a drill string, and the drill bit is caused to rotate by rotation of the drill string, which is rotated by appropriate means on the drilling rig. The drill string hangs from the rig and is in tension, but in order to apply the necessary weight to cause the drill bit to bite into the earth, a bottom hole assembly is disposed just above the drill bit. The bottom hole assembly that applies weight to the drill bit is, in effect, a number of weighted drill collars.
The drill string is made up of numerous drill pipes joined end-to-end, and each of the drill pipes might be about thirty feet in length. Usually the pipes are slightly enlarged in their end regions to provide for connection components to enable one end region of a drill pipe to be connected to the adjacent end region of the adjacent drill pipe. Further, the drill pipes are hollow and thus provide a continuous channel of communication between the drill rig and the bottom of the wellbore, down through which a suitable drilling fluid can be introduced to the region around the drill bit.
Extended reach drilling, which can mean that the drill bit can be at a position several miles laterally displaced from the foot of the rig, and horizontal drilling, which is drilling where the bit is caused to follow an arcuate route and then drill a horizontal bore and is a technique used to complete wells once the bits are in the reservoir, are types of drilling commonly used in the oil-field industry. In both extended reach drilling and horizontal drilling, transmission of power from the rig to the drill bit may be hindered due to the frictional losses experienced between contact between the enlarged connected end portions of the drill pipes and the edges of the wellbore.
Often the wellbore is lined with a casing and, to protect the drill string from abrasion against the side wall of the wellbore or the casing, a drill pipe protector can be employed. The purpose of the drill pipe protector is to keep the pipe from contacting the casing or walls of the wellbore. Without a drill pipe protector, contact between the drill string and the casing and wellbore creates frictional torque and drag. A considerable amount of torque can be produced by the effects of frictional forces developed between the rotating drill pipe and the casing or the side wall of the wellbore. Thus, without a drill pipe protector, additional torque is required while rotating the drill string to overcome this resistance. In addition, the drill string is subjected to increased shock and abrasion whenever the drill string comes into contact with the side wall of the wellbore or the casing.
There have been attempts to make drill pipe protectors that are non-rotating with respect to the side wall of the wellbore or casing. In other words, drill pipe protectors may remain in fixed contact with the casing or side wall of the wellbore and not rotate with respect thereto, which means that the drill string must rotate with respect to the drill pipe protector. Rotation of a drill pipe protector with respect to the drill string may still create frictional torque and drag on the drill string. Additionally, rotation of the drill pipe protector with respect to the drill string may lead to wear and abrasions on the outer surface of the drill pipes of the drill string, and thus, may lead to a shorter life span.